701 Motor Protection Relay Date Code 20010719
Settings Calculation
Basic Motor Protection
4.22
You can view the present learned thermal capacity to start using the serial port
MOTOR command or the front-panel Motor Statistics\Average and Peak Data
Function (see Figure 5.29 on page 5.19 in Section 5: Front-Panel Operation).
Motor Cooling Time Settings
Table 4.13 Mot or Cooling Time Settings
A stopped motor may take longer to cool than a running motor due to reduced
airflow or loss of forced coolant. The factory default settings assume that the motor
stopped cooling time is twice the motor running cooling time. Based on the setting
names, the equation is:
Equation 4.1
You can take similar steps to calculate the COOLTIME setting for
your application.
Motor running and stopped cooling times or time constants may be provided by
the motor manufacturer. If a time constant is provided, multiply that value by 3 to
calculate the Motor Stopped Cooling Time (COOLTIME) setting.
When the relay is monitoring one or more RTDs in the motor windings and an
ambient temperature RTD, the relay can learn the stator cooling time by monitoring the
winding temperature when the motor is stopped. If you set Use Learned Cooling
Time equal to Y, the relay learns the cooling time over five stops and uses it in the
thermal model in place of the Motor Stopped Cooling Time setting. When you apply
the user-defined curve Thermal Element Setting Method (SETMETH = USER), the
rotor and stator cooling time constants for the motor may be significantly different.
Therefore, Use Learned Cooling Time should be disabled (COOLEN = N) in this case,
unless a cooling time or time constant is recommended by the motor manufacturer.
Table 4.13 Motor Cooling Time Settings
Setting Prompt
Setting Range
Setting Name =
Factory Default
Motor Stopped Cooling Time 180–72000 s COOLTIME = 259
Use Learned Cooling Time Y, N COOLEN = Y
COOLTIME 2 9 LRTCOLD LRTHOT–()•
LRA
FLA
------------
èø
æö
2
••=
292.52.1–()•
30.00
5.00
-------------
èø
æö
2
••=
259 s=
To Next Page
Loading...
